Overall I had a very good stay and would give 4.5 stars.
Location - Fantastic. Near the BTS, near restaurants, 30s walk from 7-Eleven, easy to get taxis, quiet but central. Couldn't be a better location!
Apartment - The sitting room and bedroom are furnished very nicely, and are very comfortable. The bathroom and kitchen feel much older and not as nice, but they're fine, and you'll spend most of your time in the bedroom and sitting room anyway.
Bed - The mattress is very firm. It will suit some people but not others.
Facilities - The pool was nice. Gym looked okay. Didn't really use either. Security wasn't an issue, and I was never asked if I'm an AirBNB guest or anything like that. Didn't have any issues coming and going.
Host - Jing was very nice and easy to reach. I got locked out once and she was helpful. She also gave good advice re my visa extension, which I appreciated.